Light guide plates can emit incident light substantially uniformly from a comparatively wide light emitting surface and are therefore employed in liquid crystal display devices, illumination devices, etc. When light from a light source enters a light incident surface on one side of a light guide plate, the light repeats reflection on a pair of principal surfaces of the light guide plate to propagate within the light guide palate in a direction (propagation direction) substantially orthogonal to the light incident surface. The light propagating in the light guide plate is emitted little by little from the light emitting surface by an optical operation as it propagates. It is noted that in typical liquid crystal display devices, a diffuser plate is provided between the light guide plate and a liquid crystal display element, thereby irradiating the light from the light source uniformly to the liquid crystal display element.
It has been known that a pattern of dots, in which the areas of the dots increase away from the light incident surface, is provided on a principal surface of the light guide plate (Patent Literatures 1 and 2). Patent Literature 1 discloses that a pattern of circular dots is formed on an emission surface or a surface opposite to the emission surface. Further, Patent Literature 2 discloses that projections and recesses are formed in an emission surface or a surface opposite to the emission surface with the use of a mold.